[lug] Debugging a startup problem

[Jed S. Baer]

On Mon, 30 Jul 2018 00:17:15 -0600
Lee Woodworth wrote:

> RE: if renaming, with newer kernels+udev there is something
> related to persistent interface naming where udev will rename
> eth0 to a bus/slot/function related name (e.g. enps3). Do you
> ever see names like that in dmesg? Is there a way see if any
> systemd service/unit is renaming the interface? BTW udev appears
> to have been taken over by systemd as the daemon binary is
> /lib/systemd/systemd-udevd using the standard udev package.

Yes:

r8169 0000:01:00.0 eth2: renamed from eth0
systemd-udevd[586]: renamed network interface eth0 to eth2

While this system is using upstart as init, it does have some of the
systemd stuff.

> When you say 'network doesn't come up', do you mean the nic's
> link isn't detected, it doesn't have any addresses/routes or
> it had a link and address but was shutdown?

Dev eth2 is not present in the output of ifconfig. network-manager is in
a stop/waiting state. Issuing service network-manager start (or restart)
clears this up, and network-manager brings up the eth2 device.

> What happens when
> you do: ip link set dev ethX up? (e.g. does it come up but
> systemd or xxx then shuts it down)

When I'm next in a position where I feel like messing with this, I'll try
that.

I'm reminded of how, some years ago, when network-manager first landed in
an install I did, it was a simple thing to just remove it, and start the
network the SysV way, and I did that. These days, it's so wrapped up in
dependencies that apt complains about a lot of stuff if I try to get rid
of it. Hey, let's look in /etc/init.d/networking !!!

case "$1" in
start)
    if init_is_upstart; then
        exit 1

No! Silly user! You will not try to subvert our decisions for how your
system runs!